Electric signal and control device



' June 4, 1935- k c. B. BARTLEY 5 ELECTRIC SIGNAL AND CONTROL DEVICEFiled Feb. 26, 1931 INVENTOR 021 V 427% mm FM in Patented June 4, 1935UNITED STATES PATENT OFFICE 2 Claims.

My invention relates to a system for indicating the condition of anelectric circuit and for controlling the circuit under certainconditions.

5 One object of my invention is to provide an improved form of pilotsignal for indicating the location of a control switch, as well as thecondition of a circuit controlled thereby.

A further object of the invention is to provide load-limiting means inthe form of a circuit interrupter for opening a circuit upon theoccurrence of a fault therein and maintaining the circuit open untilmanually reclosed.

A still further object of the invention is to provide a novel form ofinterrupter device embodying a current transformer and circuitinterrupter in one unit.

For a complete understanding of the invention, reference is made to theaccompanying drawing illustrating a preferred embodiment thereof. Thesingle figure of the drawing is a diagrammatic showing of the invention.As shown in the drawing, a current transformer has a core of C or Ushape, that is, with one leg open. The air gap across this opening isadapted to be closed by a leg 2| pivoted to the core of the transformerand having contact members cooperating therewith. The transformer 20 hasa primary winding connected in series with a switch 22 and a load device23. The contacts on the pivoted leg 2| are also in circuit with the loaddevice.

A latch 24, is provided on the transformer core for locking the pivotedleg 2| in closed position, although this is not essential.

Across the contacts of the leg 2|, which constitute a circuitinterrupter, I connect a choke coil having a high impedance, thefunction of which will appear presently. The secondary winding of thetransformer 20 is connected to a current consuming device 26.

Normal operation of the device 23 may be initiated by closing the switch22. Current is thus supplied from a source to the device 23 through theswitch 22 and the contacts of the circuit interrupter 2|. Aglow-discharge device 21 is employed to indicate the condition of thecircuit and the position of the switch 22. The glow lamp 2! may beplaced at any desired position to indicate the condition of the circuitincluding the device 23. The lamp may be placed adjacent the transformerswitch to indicate the location thereof or may be positioned at anyother desired point. If the lamp is positioned adjacent the switch, itserves not only to indicate the condition of the circuit but theposition of the switch. As long as the circuit, including the device 23,is complete, the lamp 2'! will glow if the switch 22 is open. When theswitch I2 is open, therefore, the energization of 5 the lamp 2'!indicates that the circuit, including the device 23, is in normaloperative condition. When the switch 22 is closed, the lamp 2! isshunted and extinguished. Under normal operating conditions, the air gapin the mag netic circuit of the transformer 20, which exists when theleg 2| is in the position shown, is sufficient to prevent the primarywinding of the transformer from setting up sufficient flux in themagnetic core to introduce any appreciable 15 reactance in the circuitof the device 23.

If an excessive current is drawn by the device 23, however, the fluxinduced in the transformer 20 will be sufiicient to attract the pivotedleg 2| and thereby open the circuit. The latch 24 becomes effective tohold the circuit open until manually reset. When the leg 2| is attractedto the dotted line position, the reluctance of the magnetic circuit inthe core 20 is very much decreased and the flux produced in the primarywinding is likewise increased. This causes the transformer 20 to have agreater reactance and so effect a choking action on the over-loadcurrent. It also holds the leg 2| closed until the overload is removed,so that the latch 24 may be dispensed with, if desired. The choke 25prevents excessive arcing at the contacts opened by the movement of theleg 2| and has a sufficiently high impedance to prevent flow ofappreciable current through the device 23 when the circuit has beenopened at the circuit breaker 2|. The current consuming device 26 may beso selected or adjusted that the desired operation of the pivoted leg ofthe transformer 20 will result. The secondary winding of the transformerexerts a demagnetizing effect on the core thereof, so that by adjustingthe value of the impedance of the device 26, the exact value of thecurrent at which the circuit interrupter will open may be varied.

Numerous advantages characterize the invention' described herein. In thefirst place, an inexpensive pilot signal is provided to indicate thecondition of a circuit or the position of a switch. This signal consumesan almost negligible current and provides an effective indication at alltimes. The current transformer and the load-limiting device or circuitinterrupter provides simple but efficient means for opening a circuit incase of over-load and interrupting the 55 be limited by the disclosuresince any changes. in the latter may be made within the scope of thefollowing claims.

I claim:

1. A device for protecting a circuit from ex-' cessive overloadcomprising a-magnetic core having a movable armature adapted to closethe, core, a primary exciter winding on said core adapted to beconnected in series with the load on said circuit, said movable portionnormally shunting a circuit adapted to be connected in series with theprimary and load on movement of said portion, and a secondary winding onsaid core connected to a resistor of such value as to cause the primarywinding to maintain sufficient excitationrof said core to hold saidmovable portion attracted after it is once actuated by the building upof flux in the core due to increased current through said load.

2. A device for protecting a circuit from excessive overload comprisinga'magnetic core having a movable portion adapted to close the core, aprimary exciting winding on said core adapted to be connected in serieswith the load on said circuit, and a secondary winding on said coreconnected to a resistor of such value as to cause the primary winding tomaintain sufiicient excitation of said core to hold said movable portionattracted after it is once actuated on the building up of flux in thecore due to increased cur- 20

